Monolithic AC/DC Converter for Generating DC Supply Voltage

ABSTRACT

An integrated circuit (IC) comprises a rectifier/regulator circuit coupled to receive an ac source voltage and output a regulated dc voltage. The rectifier/regulator circuit includes first and second switching elements that provide charging current when enabled. The first and second switching elements do not provide charging current when disabled. A sensor circuit is coupled to sense the regulated dc voltage and generate a feedback control signal coupled to the rectifier/regulator circuit that enables the first and second switching elements when the regulated do voltage is above a target voltage, and disables the first and second switching elements when the regulated do voltage is below the target voltage.

This application is a continuation of application Ser. No.: 12/1587,398,filed Oct/ 6, 2009, now U.S. Pat. No. 8,634,218, which is assigned tothe assignee of the present application.

TECHNICAL FIELD

The present disclosure generally relates to the field of integratedcircuits, and more particularly to an integrated circuit for generatinga regulated dc supply voltage from an ac line voltage.

BACKGROUND

An integrated circuit typically requires a regulated dc supply voltagefor operation. This regulated dc supply voltage is typically derivedfrom an ac line voltage via external circuit components arranged toimplement a discrete rectifier. Existing rectifier circuits such ashalf-bridge or full-bridge rectifier circuits are usually implementedwith discrete diodes. A separate stage of regulation circuitry typicallyincludes discrete components, such as a capacitor, to provide regulationto the dc voltage received from the rectifier. The use of discretecomponents increase material costs and require additional space on aprinted circuit board (PCB) to provide the regulated dc supply voltagefor an integrated circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and notlimitation, in the figures of the accompanying drawings, wherein:

FIG. 1 illustrates an example block diagram of a monolithic ac/dc powerconverter for generating a dc power supply voltage on an integratedcircuit (IC).

FIG. 2 illustrates an example conceptual circuit schematic diagram ofthe monolithic ac/dc power converter circuit shown in FIG. 1.

FIG. 3 illustrates an example detailed circuit schematic diagram of themonolithic ac/dc power converter circuit shown in FIGS. 1 & 2.

DESCRIPTION OF EXAMPLE EMBODIMENTS

In the following description specific details are set forth, such asmaterial types, voltages, component values, configurations, etc., inorder to provide a thorough understanding of the present invention.However, persons having ordinary skill in the relevant arts willappreciate that these specific details may not be needed to practice theembodiments described.

It should be understood that the elements in the figures arerepresentational, and are not drawn to scale in the interest of clarity.It is also appreciated that although an IC utilizing N-channelfield-effect transistor devices is disclosed, P-channel transistors mayalso be utilized in alternative embodiments. In still other embodiments,some or all of the metal-oxide-semiconductor field-effect transistor(MOSFET) devices show by way of example may be replaced with bipolarjunction transistors (BJTs), insulated gate field effect transistor(IGFETs), or other device structures that provide an active switchingfunction. Furthermore, those with skill in the art with integratedcircuits and power converter devices will understand that transistordevices such as those shown by way of example in the figures may beintegrated with other transistor device structures, or otherwisefabricated or configured in a manner such that different devices sharecommon connections and semiconductor regions (e.g., N-well, substrate,etc.).

In the context of the present application, when a transistor is in an“off state” or “off” the transistor is unable to conduct current.Conversely, when a transistor is in an “on state” or “on” the transistoris able to conduct current. In one embodiment, a high-voltage transistorcomprises an N-channel metal-oxide-semiconductor field-effect transistor(MOSFET) with the high-voltage being supported between the firstterminal, a source, and the second terminal, a drain.

For purposes of this disclosure, “ground” or “ground potential” refersto a reference voltage or potential against which all other voltages orpotentials of a circuit or IC are defined or measured.

FIG. 1 illustrates an example block diagram of an ac/dc power converterfor generating a dc power supply voltage on an integrated circuit (IC)100. As shown, IC 100 includes a rectifier/regulator circuit 101 coupledto receive an externally-generated ac input voltage, V_(IN), appliedacross input terminals or pins 114 & 115. In one example, input voltage,V_(IN), may be an ordinary ac line voltage (e.g., 85 V ac-265 V ac;50-60 Hz). In another example, IC 100 may be implemented in a threephase system. In another example, IC 100 may be a monolithic IC. Asshown, rectifier/regulator 101 functions to provide rectification to theac input voltage V_(IN) and regulate an output voltage V_(OUT) acrossterminals 111 and 112. Stated differently, the ac input voltage V_(IN)is converted to a dc output voltage V_(OUT), such that the polarity ofthe output signal remains unchanged (positive).

As shown, sensor circuit 102 is coupled between terminals 111 and 112 toreceive the dc voltage output from rectifier/regulator circuit 101 andto output a feedback signal FB in response to dc output voltage V_(OUT),provided across output terminals 111 and 112. By way of example,regulated dc voltage V_(OUT) may be configured as a supply voltage of alow voltage (e.g., 5 V) at terminal 111 with respect to terminal 112 atground (0 V). It is appreciated that the output voltage V_(OUT),produced across output nodes 111 and 112, may be used as a supplyvoltage for operation of circuitry internal to IC 100. In anotherexample, output voltage V_(OUT) may be used for operation of circuitryexternal to IC 100.

FIG. 2 illustrates an example conceptual circuit schematic diagram of anac/dc power converter for generating a regulated dc output voltageV_(OUT) in an integrated circuit 200. As shown, integrated circuit 200includes rectifier/regulator 201 and sensor 202 which are possibleimplementations of rectifier/regulator 101 and sensor 102 respectively,of power converter 100 of FIG. 1. In this example, rectifier/regulator201 is shown comprising switching elements 204 and 205, each having oneconnection end or side respectively connected to terminals 214 and 215.As shown, switching elements 204 and 205 comprise first and secondcurrent sources 217 and 219 are coupled to receive input voltage V_(IN)from input terminals 214 and 215, respectively. As further shown,switching elements 204 and 205 further include switches SW1 and SW2 thatare coupled to current sources 217 and 219, respectively.

In one embodiment, current sources 217 and 219 are constant currentsources that selectively provide a constant charge current in responseto the polarity of the input voltage V_(IN). For example, current source217 may provide a constant charge current when the input voltage V_(IN)is at a higher potential at terminal 214 with respect to terminal 215.Similarly, current source 219 may provide a constant charge current wheninput voltage V_(IN) is at a higher potential at terminal 215 withrespect to terminal 214, In another embodiment, the magnitude of chargecurrent generated by current sources 217 and 219 may be dependent oninput voltage V.

Switches SW1 and SW2 are controlled by feedback signal FB. In operation,switching element 204 provides a constant charge current to capacitorC_(SUPPLY) when SW1 is on and current source 217 is providing chargecurrent. Switch SW1 restricts the flow of charge current from currentsource 217 in response to feedback signal FB. Similarly, switchingelement 205 provides a constant charge current to capacitor C_(SUPPLY)when SW2 is on and current source 219 is providing charge. Switch SW2restricts the flow of charge current from current source 219 in responseto feedback signal FB. In one embodiment, based on the polarity of theinput voltage V_(IN), feedback signal FB may be split into twoindependent signals independently controlling switches 204 and 205.

Rectifier/regulator circuit 201 also includes diode elements D1 and D2which have their cathodes respectively connected to input terminals 215and 214. The anodes of diodes D1 & D2 are commonly connected to groundat node 212. In one example, diode elements D1 and D2 are body diodes ofthe substrate material of integrated circuit 200. In operation, diodeelements D1 and D2 are coupled to provide a complete return path forcharge current flowing through supply capacitor C_(SUPPLY). Supplycapacitor C_(SUPPLY) is shown coupled between output nodes or terminals211 and 212 to provide a regulated output voltage V_(OUT) (dc).

Persons of ordinary skill in the art will understand that when eitherdiode elements D1 or D2 is conducting, the current flowing through D1 orD2 is a substrate current consisting of minority carriers. To preventthis substrate current from adversely affecting other circuits on IC100, ordinary double guard rails may be utilized in the layout of IC 100to confine or attenuate the substrate current. For example, in oneembodiment where IC 100 is fabricated with a P-type substrate,N+/N−-well and P+ double guard rails may be formed around the diodeelements D1 and D2. The double guard rails may be of a type ordinarilyused in electrostatic discharge (ESD) protection circuitry. It isappreciated that the size or area used to implement the double guardrails may vary in different embodiments, depending on the level ofconfinement or attenuation required. In general, a larger double guardrail area provides a higher level of confinement/attenuation.

Continuing with the example of FIG. 2, a feedback circuit 207 is showncoupled across supply capacitor C_(SUPPLY). In operation, feedbackcircuit 207 outputs a feedback signal FB in response to sensing theoutput voltage V_(OUT). Feedback signal FB is coupled to either open orclose switches SW1 and SW2. For example, during the first phase of inputvoltage V_(IN), when switches SW1 and SW2 are closed and the voltage atinput terminal 214 is high with respect to the voltage at terminal 215,current source 217 is on and a charging current is output to supplycapacitor C_(SUPPLY). In this case, the charging current flows in a paththrough supply capacitor C_(SUPPLY) and back to terminal 215 throughdiode element D1, thereby charging supply capacitor C_(SUPPLY).

Similarly, during the second phase of the input voltage V_(IN), whenswitches SW1 and SW2 are closed and the voltage at input terminal 215 ishigh with respect to the voltage at terminal 214, current source 219 ison and a charging current is again output to supply capacitorC_(SUPPLY). In this case, the charging current flows in a path throughsupply capacitor C_(SUPPLY) and back to terminal 214 through diodeelement D2, thereby charging supply capacitor C_(SUPPLY).

When the output voltage V_(OUT) is at or above the target, regulatedvalue (e.g. 5 V feedback element 207 outputs a feedback signal FB toturn off (open) switches SW1 and SW2, which prevents further charging ofsupply capacitor C_(SUPPLY) from occurring. When the voltage potentialat node 211 drops below the target, regulated value, feedback element207 outputs a feedback signal FB to turn on (close) switches SW1 andSW2, thus resuming the charging of supply capacitor C_(SUPPLY).Operation of the circuitry shown in the example of FIG. 2 may continuein this manner as long as IC 200 remains powered on.

FIG. 3 illustrates an example detailed circuit schematic diagram of anintegrated ac/dc power converter circuit 300. Integrated circuit 300 isone possible implementation of IC 100 of FIG. 1 and IC 200 of FIG. 2. Asshown, IC 300 includes a rectifier/regulator circuit 301 and sensorcircuit 302. In the embodiment of FIG. 3 switching elements 304 and 305of rectifier/regulator 301 are each shown being implemented by ajunction field effect transistor (JFET) connected to a resistor and ann-channel metal oxide semiconductor field effect transistor (MOSFET).For example, switching element 304 may comprise an N-JFET J1 having afirst terminal D (drain) coupled to input terminal 314, a secondterminal G (gate) coupled to ground node 312, and a third terminal S(source) coupled to a first end of resistor R1 and the drain of MOSFETS1. A second end of resistor R1 is coupled to the gate G of MOSFET S1.The source S of MOSFET S1 is coupled to node 311. Likewise, switchingelement 305 comprises an N-JFET J2 having a first terminal D (drain)coupled to input terminal 115, a second terminal G (gate) grounded, anda third terminal S (source) coupled to the drain of MOSFET S2, ResistorR2 is shown coupled between the gate and drain of MOSFET S2. The sourceof MOSFET S2 is coupled to node 311.

Diode elements D1 and D2 are shown having both their anodes connected toground node 312 and their cathodes respectively connected to inputterminals 315 and 314. In one embodiment, diode elements D1 and D2 areimplemented as parasitic substrate diodes; that is, a P-type substrateof IC 300 is the anode of both D1 and D2, with the cathode of each diodeelement D1 and D2 comprising the N-type drain region of the associatedJFET, J2 and J1 respectively. In other words, diode element D1 is a pnjunction comprising a P-type substrate of IC 300 and an N-type drainregion of JFET J2. Likewise, diode element D2 is a pn junctioncomprising a P-type substrate of IC 300 and an N-type drain region ofJFET J1. As described above in connection with the example of FIG. 2,double guard rails comprising N+N−well and P+ regions may be formedaround each of JFETs J1 and J2 in the layout of IC 300 to confine orattenuate the substrate current that flows through diode elements D1 andD2.

In the example of FIG. 3, each of the JFETs J1 and J2 may be integratedwith its associated MOSFET, In other words, switching elements 304 and305 may each be implemented by a single integrated device structurewhich comprises two transistor elements that share a common N-type wellregion. In one embodiment, switching element 304 may be able towithstand greater than 1000 V across the drain D of J1 and the source Sof S1, Similarly, switching element 305 may be able to withstand greaterthan 1000 V across the drain D of J2 and the source S of S2. In anotherexample, JFETs J1 and J2 may be part of a separate high voltage circuitand/or device that performs a different function on IC 300.

In the embodiment of FIG. 3, voltage sensor circuit 302 comprises asupply capacitor C_(SUPPLY) connected across output terminals 311 and312. Voltage sensor circuit 302 further comprises a comparator 320configured with the negative input coupled to a voltage reference,V_(REF), and the positive input connected to a node 321. Node 321provides a feedback voltage V_(FB) with respect to ground terminal 312,In the example shown, feedback voltage V_(FB) is representative ofregulated output voltage V_(OUT) and is generated from a resistordivider network comprising resistors R3 and R4 coupled in series acrossoutput terminals 311 and 312. In operation, the output signal, FB,generated by comparator 320 drives the gates of n-channel MOSFETs S3 &S4. The sources of MOSFETs S3 & S4 are coupled to ground terminal 312.The drains of MOSFETs S3 & S4 are respectively connected to the gates ofMOSFETs S1 & S2. In one embodiment, MOSFETs S3 and S4 are level shiftersthat control the voltage at the gates of MOSFETs S1 & S2, therebyallowing switches S1 and S2 to turn on and off.

In operation, voltage sensor 302 operates by comparing the voltageV_(FB) appearing at node 321 against reference voltage V_(REF). In oneembodiment, the value of resistors R3 and R4 are selected in order toregulate output voltage V_(OUT) at a desired target value,. When thevoltage at node 321 exceeds the voltage reference V_(REF), thusindicating that output voltage V_(OUT) has exceeded its target,regulated value, comparator 320 switches MOSFETs S3 and S4 on, whichturn MOSFETs S1 and S2 off, thereby disabling switching elements 304 and305. Conversely, when the voltage V_(FB) at node 321 drops belowV_(REF), due to output voltage V_(OUT) dropping below its target,regulated value, the output of comparator 320 drops low, causing MOSFETsS3 & S4 to turn off. When both MOSFETs S3 & S4 are in an off state,switching element 304 or switching element 305 conducts charge current,depending on the polarity of the input ac voltage V_(IN).

When the voltage potential at terminal 314 is high with respect toterminal 315, switch 304 is conducting and switch 305 is not conducting,and supply capacitor C_(SUPPLY) is charged by the current flowing fromterminal 314 through JFET J1, MOSFET S1, and supply capacitorC_(SUPPLY), and back through diode D1 to terminal 315. On the otherhand, when the voltage potential at node 315 is high with respect tonode 314, switch 304 is not conducting, switch 305 is conducting, andsupply capacitor C_(SUPPLY) is charged by the current flowing fromterminal 315 through JFET J2, MOSFET S2, and supply capacitorC_(SUPPLY), and back through diode D2 to terminal 314,

Although the present invention has been described in conjunction withspecific embodiments, those of ordinary skill in the arts willappreciate that numerous modifications and alterations are well withinthe scope of the present invention. Accordingly, the specification anddrawings are to be regarded in an illustrative rather than a restrictivesense.

1-15. (canceled)
 16. An integrated circuit (IC) comprising: a regulatorcircuit coupled to receive an ac source line voltage of between 85 to265 V AC across first and second input terminals and output a regulateddc supply voltage across first and a second output terminals, theregulator circuit including first and second high-voltage switchingelements that selectively provide charging current when enabled, thefirst and second high-voltage switching elements capable of supporting avoltage difference between the ac line voltage and the regulated dcsupply voltage; and a sensor circuit coupled to sense the regulated dcsupply voltage and generate a feedback signal to control the first andsecond high-voltage switching elements, wherein the feedback signalturns off the first and second switching elements when the regulated dcvoltage is above a target voltage, and turns on the first and secondswitching elements when the regulated dc voltage is below the targetvoltage.
 17. The IC of claim 16 wherein the first and second switchingelements are respectively coupled to first and second input terminals.18. The IC of claim 16 wherein the sensor circuit includes a supplycapacitor coupled between the first and second output terminals,
 19. TheIC of claim 18 wherein the sensor circuit further includes: a voltagedivider coupled between the first and second output terminals, thevoltage divider generating a feedback input voltage from the regulateddc voltage; and a comparator that generates the feedback signal bycomparing the feedback input voltage to a reference voltage.
 20. The ICof claim 18 wherein the first high-voltage switching element includes: afirst MOSFET coupled between the first input terminal and the firstoutput terminal and a first junction field-effect transistor (JFET)coupled between the first input terminal and a drain of the firstMOSFET; and further wherein the second high-voltage switching elementincludes: a second MOSFET coupled between the second input terminal andthe first output terminal; and a second JFET coupled between the secondinput terminal and a drain of the second MOSFET.
 21. The IC of claim 20further comprising first and second body diodes each having an anodecoupled to the second output terminal, a cathode of the first body diodebeing coupled to the second input terminal and the cathode of the secondbody diode being coupled to the first input terminal, the cathode of thefirst body diode comprising a common well region shared by the secondMOSFET and second JFET, the cathode of the second body diode comprisinga common well region shared by the first MOSFET and first JFET, acharging current of the supply capacitor alternately flowing through thefirst body diode when the first high-voltage switching element is turnedon and through the second body diode when the second high-voltageswitching element is turned on.
 22. The IC of aim 16 wherein theregulated do supply voltage is a 5V dc supply voltage.
 23. An integratedcircuit (IC) comprising: a regulator circuit coupled to receive an acvoltage and output a regulated dc supply voltage, the regulator circuitincluding: first and second high-voltage switching elements that whenenabled selectively provide charging current to a supply capacitoracross the regulated dc supply voltage, the first and secondhigh-voltage switching elements being respectively coupled to first andsecond input terminals; and a sensor circuit coupled to sense theregulated do supply voltage and generate a feedback control signaltherefrom, the feedback control signal being coupled to enable the firstand second high-voltage switching elements to conduct current when theregulated dc supply voltage is below a target voltage, and to disablethe first and second high-voltage switching elements from conductingcurrent when the regulated dc supply voltage is above the targetvoltage, wherein the first high-voltage switching element is conductingwhen a potential difference between the first and second input terminalsis positive and the first high-voltage switching element is enabled, thefirst switching element not conducting when the potential difference isnegative and the first high-voltage switching element is enabled, thesecond high-voltage switching element conducting when the potentialdifference is negative and the second high-voltage switching element isenabled, the second high-voltage switching element not conducting whenthe potential difference between the first and second input terminals ispositive and the second high-voltage switching element is enabled. 24.The IC of claim 23 wherein the IC is a monolithic power IC.
 25. The ICof claim 23 wherein the first and second high-voltage switching elementsare respectively coupled to the first and second input terminals. thefirst and second input terminals being coupled to receive the ac linevoltage.
 26. The IC of claim 23 wherein the sensor circuit includes thesupply capacitor coupled to the rectifier/regulator circuit and theregulated dc supply voltage being generated across the supply capacitor.27. The IC of claim 26 wherein the sensor circuit further includes afeedback circuit that regulates charging of the supply capacitor tomaintain the regulated dc supply output voltage.
 28. An integratedcircuit (IC) for generating a regulated dc supply voltage at a supplynode from an ac input voltage comprising: a regulator circuit coupled toreceive the ac input voltage across first and second input terminals,the rectifier/regulator circuit including: a first high-voltageswitching element which includes a first transistor coupled between thefirst input terminal and the supply node; a second switching elementwhich includes a second transistor coupled between the second inputterminal and the supply node; and a sensor circuit coupled between thesupply node and a reference node, the sensor circuit being operable tosense the regulated dc supply voltage at the supply node and generate afeedback signal therefrom, the feedback signal being coupled to controlthe first and second switching elements; wherein the feedback signaldisables the first and second switching elements from providing chargingcurrent to the supply node when the regulated dc supply voltage is abovea target voltage, and enables the first and second switching elements toprovide charging current to the supply node when the regulated do supplyvoltage is below the target voltage, and wherein the first high-voltageswitching element is conducting when a potential difference between thefirst and second input terminals is positive and the first high-voltageswitching element is enabled, the first high-voltage switching elementis not conducting when a potential difference between the first andsecond input terminals is negative and the first high-voltage switchingelement is enabled, the second high-voltage switching element isconducting when a potential difference between the first and secondinput terminals is negative and the second high-voltage switchingelement is enabled, the second high-voltage switching element is notconducting when a potential difference between the first and secondinput terminals is positive and the second high-voltage switchingelement is enabled.
 29. The IC of claim 28 wherein the regulator circuitfurther includes first and second substrate diodes each having an anodecoupled to the reference node, a cathode of the first substrate diodebeing coupled to the first input terminal and a cathode of the secondsubstrate diode being coupled to the second input terminal, the chargingcurrent alternately flowing through the first and second substratediodes when the first and second transistors are enabled.
 30. The IC ofclaim 28 wherein the first high-voltage switching element furtherincludes a junction field-effect transistor (JFET) coupled between thefirst input terminal and a drain of the first transistor, the secondhigh-voltage switching element further including a second JFET coupledbetween the second input terminal and a drain of the second transistor.31. The IC of claim 28 wherein the sensor circuit further includes asupply capacitor coupled between the supply node and the reference node.32. The IC of claim 28 wherein the sensor circuit further includes: avoltage divider coupled between the supply node and the reference node,the voltage divider generating a feedback voltage from the regulated dcsupply voltage; and a comparator that generates the feedback signal bycomparing the feedback voltage to a reference voltage.
 33. The IC ofclaim 28 wherein the anode of the first and second substrate diodescomprises a P-type substrate of the power IC, the cathode of the firstsubstrate diode comprising a N-type well region of the first transistor,the cathode of the second substrate diode comprising a N-type wellregion of the second transistor.